FR2669969A1 - GEAR PUMP FOR A DEVICE FOR DISPENSING A DOSED QUANTITY OF A LIQUID. - Google Patents

Abstract

A gear pump (20) for use in a metered quantity dispenser of a liquid includes a pair of carbon graphite wear plates (69, 70) to increase the suction head of the pump. The wear plates are disposed on opposite sides of the spur gears (55, 56) of the pump and are biased against the sides of the gears to reduce internal clearances of the pump. The biasing force is provided by a resilient seal placed between a surface of the pump body and one of the wear plates. The gears are mounted to have limited movement so that the stress from one of the wear plates is transferred through the gears to the other plate. The gear pump is driven through a reduction gear (22) by a reversible electric motor (21). The use of a gear pump ensures precise metering of the amount of fluid supplied by the device.

Description

1 2669969

  The present invention generally relates to a device for dispensing a metered amount of a liquid and, more particularly, to a positive displacement gear pump for use in such a device. Chemical treatment of crops is carried out in agriculture Two main areas in which chemical treatments are used are fertilization and insect control In order to minimize distribution costs, chemicals are generally sold to distributors in bulk quantities of a concentrated liquid The distributor then supplies the farmer with smaller quantities of the concentrate by pumping the necessary quantity from a bulk storage tank The farmer adds water in order to dilute the chemicals to obtain the correct concentration before their application

to his crops.

  To get the maximum effect from the chemical without damaging the crops, the amount of the chemical used is extremely critical The manufacturer of the chemical will specify the desired ratio of the chemical to the water to be used The total amount of the chemical needed is then calculated and distributed in relation to the total volume of the farmer's container In addition, as the chemicals are concentrated, they are very expensive Thus, an accurate measurement of the quantity supplied to the farmer is important Handling must be done with care because, in the concentrated state, the chemicals could have an adverse effect on the environment and anyone in

contact them in the event of a leak.

  The present invention relates to an improved gear pump, which has wear plates arranged against the opposite sides of a pair of spur gears and biased against the sides of the

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  gears so as to minimize the internal clearances of the pump This results in the possibility of having a greater head at suction or vacuum The wear plates are made of carbon graphite which allows initial dry operation of the pump without

additional lubrication.

  The spur gears of the pump are contained in the pump body One of the wear plates is "fixed" while the other is pressed against the spur gears by an O-ring The spur gears are mounted so as to undergo a limited axial displacement, so that the biasing force exerted by the O-ring against the "movable" wear plate also stresses the

  gears against the fixed wear plate.

  The gear pump is specially designed for use in a device for dispensing a metered amount of a liquid, and provides precise dosing of the pumped liquid. The gear pump is driven by a gearbox by a reversible motor. , and can operate in reverse to cause defusing of a liquid discharge hose The revolutions of the gear pump are monitored by a passive magnetic sensor The sensor produces a signal which is used by an electronic control to calculate the volume total liquid displaced by the pump The electronic control also controls the

  drive motor operation.

  The present invention will be well understood

  during the following description made in connection with

  the accompanying drawings in which: FIG. 1 is a diagram of a device for

  distribution according to the present invention.

  Figures 2a and 2b are flowcharts showing the operation of the dispensing device.

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  Figure 3 is a plan view of the electronic control keyboard used to make

operate the device.

  Figure 4 is a diagram of an alternative embodiment of the dispensing device which comprises means for returning the liquid from the flexible

  discharge to the supply tank.

  Figure 5 is a diagram of another variant of the dispensing device which comprises a means for recirculating the liquid by

  through the feed tank.

  FIG. 6 represents yet another variant of the dispensing device in which a ventilation valve, actuated by float, serves to

  detect the priming of the device.

  Figure 7 is a diagram of an alternative embodiment of the dispensing device which comprises a foot valve of the suction probe and a valve

  for the return of the liquid.

  Figure 8 is a section (taken generally along line 8-8 of Figure 10 of a gear pump and a pump body suitable for use with the device of the present invention. Figure 9 is a end section view (taken along line 9-9 of Figure 8) of the

gear pump of figure 8.

  Figure 10 is a sectional view taken on

  along line 10-10 of Figure 8.

  Figure 11 is a sectional view taken on

  along line 11-11 of Figure 8.

  Figure 12 is a perspective view of a first type of a wear plate used in the pump

with gears of figures 8 to 11.

  Figure 13 is a perspective view of a second type of wear plate used in the pump.

gear of Figures 8 to 11.

  Figure 14 is a top plan view of a throttle valve of the type used in the "return drain" delivery device of Figure 4 which includes an integral vacuum rupture valve. Figure 15 is a partial sectional view, on a large scale, taken along line 15-15 of the

figure 14.

  In Figure 1, there is shown a device for dispensing a metered amount of a liquid, shown in broad outline by the reference 10, according to the characteristics of the present invention In Figure 1 and in the other diagrams, the electrical connections / magnetic and / or couplings between components are represented by dashed lines, while the liquid connections or lines are represented by solid lines The liquid, often a concentrated chemical, is kept in a tank or container. feed 11 which could consist of any one of a large number of devices including a tank mounted on a truck or an easily transportable 40 liter container The feed container 11 comprises a coupler 12 with low flow and an atmospheric vent 13 The vent 13 is provided with an air outlet filter 14 so as to prevent droplets of liquid suspended in the air from escaping towards the atmosphere The coupler 12 can be of the type described in United States patent application No. 494,644, filed March 16

  1990 and which is incorporated here for reference.

  The liquid in the feed container 11 is pumped by a positive displacement gear pump 20 The pump 20 is driven by a reversible motor 21 by means of a reduction gear 22 A gear ratio is chosen for the reduction gear 12 which allows the speed of the motor to be adapted to the needs of the pump While the motor can be any motor that is commercially available, a 12 volt direct current motor is convenient when used with a distribution device mounted on a vehicle such as a truck because it will be compatible with the system

vehicle.

  The liquid is extracted from the container 11 by a suction hose 23 by the pump 20 and is then introduced into a discharge hose 24 to a throttle valve 25, which is connected to a low flow distribution coupler 26 La valve 25 includes an anti-siphon check valve 27 which is generally connected directly to the coupler 26 to prevent return into the hose 24 The liquid is discharged into the receptacle 28 of the user, which may also include an atmospheric vent 28 a Le receptacle 28 can correspond to any one of a certain number of devices. For example, it can be the supply tank of an agricultural sprayer pulled by a tractor. Water is generally added to receptacle 28 so dilute chemicals and achieve a concentration that will be applied safely to crops Electric power is supplied to the engine and other components ts of the transfer device by an external power supply 29, such as a battery, by

example.

  The dispensing operation is controlled by an electronic control 30 based on a microprocessor, which can be mounted directly on the assembly formed by the gear pump and the motor.

  or be secured with a cable harness.

  The user enters the specific data relating to a particular distribution operation in the control 30 by means of a keyboard 31 The control 30 also comprises an alphanumeric liquid crystal display device 32 so as to notify the user of the associated program, and provide it with information during the distribution operation As will be discussed, the command 30

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  monitors various operating parameters of the system and controls the running of the motor 21 so as to obtain

  a pre-programmed distribution operation.

  As the gear pump is of the positive displacement type, a fixed volume of liquid, known with precision, is displaced during each revolution or

  fraction of a turn of the pump drive shaft.

  According to the present invention, a transducer 33 is coupled so as to detect the rotation of a rotating element in the assembly formed by the gear pump / the reducer / the motor. For example, the transducer 33 can detect the rotation of the gear pump drive shaft by counting the teeth of a drive gear or target wheel, and

  provide this information to the electronic control 30.

  As soon as the device is primed, the control is then able to precisely control the quantity of liquid dispensed by monitoring the rotation of the drive shaft. The transducer can correspond to one of several well-known configurations, such as, for example, a passive variable reluctance magnetic transducer, or a Hall effect device. A device 35 for detecting liquid is incorporated in the throttle valve 25 so as to signal to the control 30 the moment when the initiation has been established in the discharge hose 24 The device 35 may be, for example, a switch to blade which responds to the movement of a magnet carried by the check valve 27 which is designed to actuate the blade switch only upon detection of the flow of liquid During the priming of the discharge hose, while the air present in the hose 24 is driven in the throttle valve 25, no liquid will be present in the valve, and the reed switch will not be actuated, hence the signal to the electronic control that there is discharge no liquid Electronic control 30 will not count liquid

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  pumped during the priming operation as part of the quantity to be supplied As soon as the liquid is present, the reed switch will be actuated, and the electronic control will start to monitor the quantity of the liquid which is pumped In addition, in case presence of an air pocket in the discharge hose 24 during a dispensing operation, the reed switch will become unactuated so that there is signaling to the electronic control of this situation, and this air volume will not be applied to the

quantity that we want to distribute.

  It will be noted that, while the liquid detection device is shown in FIG. 1 as being wired directly to the electronic control 30, it may be desirable in certain cases to use a "wireless" connection. In this case, the valve to throttle 25 will carry a small battery operated transmitter, and a receiver will be located in

electronic control 30.

  We will now describe in detail the operation of the typical dispensing device for a typical user, in conjunction with the flowcharts of FIGS. 2 a and 2 b, as well as with the keyboard diagram of FIG. 3 and the diagram of FIG. 1 L user begins by connecting the distribution coupler 26 to its receptacle 28 (see FIG. 1) Then, as shown in the step of FIG. 2 a, he connects the power supply by connecting the device to the source 29 When receiving the energy, the electronic control 30 initializes a series of device integrity tests at a step 101 First, there is execution of a series of self-diagnostic tests If one of the diagnostics is not satisfied, an error message is displayed (as shown in Figure 3) on the upper line 32 a of the display device 32 and the control 30 is invalidated If the device is equipped with an optional reset valve outstanding (described below in connection with Figure 5), the valve is checked at 102 so as to ensure that it

  is in the distribution position.

  Then, the device is checked at 103 as to its priming. Before recording the pumped quantity of the liquid, the discharge hose 24 must be primed. This hose can be long enough, as is necessary for transferring liquid between a truck. feed and farm machinery located in a field The liquid detection device 35 serves, as indicated above, to signal to the control 30 the moment when the discharge hose 24 is primed. detection 35 is incorporated in the throttling valve 25, which is located at a location contiguous to the distribution coupler 26 If no liquid is present at the detection device 35, the message "NO PRIMING" will be displayed on the upper line 32 a of the display device 32, and the user will have to prime the discharge hose 24 This is done by pressing a key on the keyboard 31 which causes the pump to operate eg for a predetermined time to carry out the priming As the discharge hose 24 fills with fluid, air is moved through the valve 25 to enter the receptacle 28 of the user As soon as there is detection of the presence of the liquid, a signal is sent to the electronic control 30, the gear pump 20 is stopped and the integrity tests continue If no signal is received for a predetermined period of time for indicate that the boot has taken place, it is assumed that there has been a malfunction of the equipment, and the control 30 must stop the dispensing device As soon as there is confirmation of the boot, the main memory is checked at

step 104.

  When the integrity tests of the device have all been carried out with satisfaction, the controller will display "HOLD" on the upper line 32 a of the display device 32. If any key is pressed in a step 105, the device will display ( in 106) the last remaining quantity of the batch and the units, i.e. liters, present during the previous shutdown of the device, on the lower line 32b of the display device The user can change the units (in 107) by pressing a "UNITS" key on the keyboard 31 Another choice of units can be displayed each time the "UNITS" key is pressed The operation is repeated until the display shows desired units Any quantity of a batch indicated on the lower line 32 b will be zeroed when there is change of units The device then responds in 108 with "READY" on the upper line

  32 a of the display device.

  The user now enters (at 109) the quantity of liquid to be dispensed, which quantity will be displayed on the lower line 32 b of the display device 32 If there is an error, a correction from step 110 is easily performed in 111 by pressing the "ZERO" key on the keyboard 31 and re-entering the quantity As soon as the correct quantity has been entered, you press in 112 a "PUMP ON / OFF" key on the keyboard 31 to start transferring the liquid The control 30 again checks 113 to confirm the priming of the device If the priming has been carried out, the control 30 starts the motor 21 at 114 (in FIG. 2 b) and the pump with gear 20 starts pumping the liquid from the feed tank 11 As previously indicated, the transducer 33 detects the rotation of the drive shaft of the gear pump and transmits the information to the ordered

  electronic 30 which calculates the volume of pumped liquid.

  The quantity displayed on the lower line 32b of the display device 32 decreases in accordance

  with the received signal which comes from the transducer 33.

  Thus, throughout the duration of the transfer of the liquid, the display device 32 indicates the quantity of the liquid remaining to be transferred. The upper line 32 a of the display device will display the message "PUMPING" during the transfer of the liquid. If the device is not primed, the quantity displayed is kept constant while the gear pump 20 rotates until there is either establishment of the priming of the device, or the lapse of a predetermined period of time. In the event that the predetermined period of time elapses without the device being primed, the device is stopped in step 115 (FIG. 2 a) and a message "NO PRIMING" is displayed on the upper line 32 a of the

display 32.

  The liquid is pumped through the throttle valve 25 to enter the receptacle 28 of the user During the transfer of the liquid, the control 30 repeats continuously (at 116

  in Figure 2 b) the integrity tests that have been described below

  above Failure of any of the diagnostic tests or memory control will stop the pump and cause an appropriate error code to be displayed on the upper line 32a of the display device 32 In the event of loss of When the device is primed, the control 30 will try to restore it as described above. If the transducer 33 stops sending a signal, the display of the quantity will be kept constant for a predetermined time. transducer does not resume after this time has elapsed, the device is stopped and a message "SENSOR COUNTING" is displayed on the line

  upper 32 a of the display device 32.

  Pumping can be interrupted (at 117) at any time by pressing (at 118) a key on the keyboard 31, which has the effect of stopping the pump and freezing the display (at 119) When pressing d 'a "TOTAL" key, there will be a display of the total quantity 2669969 delivered of the liquid Pumping is resumed in 120 by pressing in 121 on the "PUMP ON / OFF" key from the supply container 11 to the receptacle 28 of the user until the total displayed on the lower line 32 b of the display device 32 reaches zero When zero is reached at 123, the command 30 will cut the power to motor 21 and

  pump 20 and the transfer cycle will be completed in 124.

  The electronic control 30 can serve other functions which are of interest to the supplier of the liquid product. The device can be recalibrated if a fluid of a different viscosity has to be pumped. To carry out this recalibration, the supplier will first press a "SECURITY" button

  keypad 31 and will then enter a pre-

  assigned which will be displayed on the lower line 32 b of the display device 32 If there is an error in the digital entry code, the supplier will press the "ZERO" key to cancel the entry and then re-enter the digital code When the code is entered correctly, the supplier presses a "CALIBRATION" key to enter the calibration data in

electronic control 30.

  The supplier can then zero a current total which is kept in the memory unit of the order This total indicates the total quantity of the liquid dispensed during several supplies Finally, the supplier can change the security code for the lowest level "CODEB" (lowest code number) to prevent unauthorized persons from changing the calibration setting or resetting the total

current that is stored.

  An alternative embodiment of the present invention is shown in Figure 4, in which the device of Figure 1 comprises means for allowing the liquid which remains in the discharge hose 24 after the metered dispensing operation

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  to be returned to the supply tank 11 This prevents contamination of the liquids (when there is passage from the supply tank to another tank with a different liquid) and moreover gives the assurance that the user will not be billed for the liquid which he did not use and which otherwise would remain in the hose 24 In order to drain the discharge hose 24, the pump is started in the opposite direction, and a modified throttle valve 25 ′ has means for introducing air into the end of the hose 24 and preventing the formation of an excessive vacuum which would stall and overload the pump motor and possibly cause the hose to be crushed In particular , as shown in FIG. 4, the valve 25 ′ comprises a vacuum breaking valve 36 which, upon detection of a positive differential pressure between the atmospheric pressure and the pressure prevailing in the hose 24, opens or will screw to allow air entry

in hose 24.

  In the unlikely event that the vacuum rupture valve 36 does not close when the device is returned to dispensing mode after drainage, the device has an additional safety feature to prevent fluid from escaping from the system. First, as shown in Figure 4, a safety check valve 37 for flow in the opposite direction is located between the vacuum rupture valve 36 and the hose 24 in order to prevent the flow of liquid at the valve 37 In secondly, in the case where the two valves 36 and 37 fail to contain fluid, an air inlet filter 38 is connected to the air inlet side of the valve 36 so as to provide sufficient limitation and prevent the fluid from escaping at a high flow rate The filter 38 also prevents contamination of the device by

  airborne particles.

  The drainage of the discharge hose 24 is controlled automatically by the electronic control. To start a "drainage" cycle, the user presses sequentially the "PUMP" and "SAFETY" 1 keys on the keyboard 31 The electronic control causes the engine to run 21 in the opposite direction, which causes the gear pump 20 to pump in the direction from the user receptacle 28 to the supply tank 11 The anti-siphon valve 27 prevents the liquid from being extract from the user's receptacle 28 When the pressure prevailing in the hose 24 drops below atmospheric pressure, the safety valve 36 opens to allow air to enter the discharge hose 24 through the intermediate of the check valve 37 while the liquid is pumped from the line 24 so that it enters the supply tank 11 The pump 20 operates in the opposite direction for a predetermined period born based on the capacity of the hose 24 During this time, the message "DRAINAGE" will appear on the display device 32 At the end of this predetermined time, the pump 20 is stopped, and the air pressure prevailing in the hose 24 will equalize with atmospheric pressure, which will cause the safety valve 36 to close. The drainage operation can be stopped at any time by the user by

  pressing any key on the keyboard 31.

  Another alternative embodiment of the invention is shown in FIG. 5, in which the device in FIG. 1 comprises a means for recirculating the liquid through the supply tank 11 so as to mix its contents carefully. The recirculation function is generally necessary when it is desired to keep microencapsulated particles which may be in suspension in the liquid. To obtain this function, a manually operated three-way valve 39, which does not dose, is inserted in the discharge hose 24 between the gear pump 20 and the throttle valve 25 The valve 39 can divert the liquid to pass it from the hose 24 into the recirculation line 40 via a recirculation coupler 41, so that it enters the supply tank 11 The coupler 41 may be of a low-flow design As the valve 39 is of the type ype without dosing, the fluid cannot flow in the hose 24 as well as in the pipe at the same instant A sensor 42 for recirculation is mounted so as to detect the moment when the valve 39 is in the return position in circulation, and signals this situation to the electronic control. The sensor can be a reed switch and a magnet which are incorporated in the structure of the valve. The recirculation mode is initiated by the operator by manually moving the valve 39

  to bring it to the recirculation position.

  When it is moved to this position, the valve 39 deflects the flow of the liquid towards the supply tank 11, and indicates to the electronic control to start the engine. In this mode, the control 30 will display the message "RESET ON CIRCULATION "and the total elapsed time of recirculation will be displayed on the display device 32 Thus, the user can follow with precision any recommendation of the manufacturer concerning recirculation times for a particular liquid While the mode recirculation is used, control 30 cannot record the quantity of fluid

which is pumped.

  When the time necessary for recirculation has elapsed, the user can return the valve 39 to its original position. When this takes place, the valve 39 returns the flow of liquid to the discharge hose 24 and the electronic control

  returns the transfer device to the "READY" state t.

  Another embodiment of the present invention is represented in FIG. 6, in which an alternative means is provided for detecting the moment when the liquid has reached the anti-siphon valve 27, indicating that the device is primed. In this embodiment, a second fluid line 43, of smaller diameter, runs along the main discharge hose 24 and is mounted between the upstream side of the valve 27 and a float type ventilation valve 44 which can be mounted on the body of the pump, and can be coupled so as to actuate a reed switch 45 which indicates to the electronic control that the device is primed An overflow line 46 is mounted between the valve 44 and the supply tank 11 When the liquid has been completely pumped into hose 24 and was returned to the pump via line 43 to raise the float and operate the reed switch 45, the control will know that the device is st primed It should be noted that, in this embodiment, the distribution coupler 26 must remain disconnected from the container 28 of the user until there is priming of the device Otherwise, during the ventilation process , liquid can be dispensed and not

  registered, and the device will not vent from itself

  even as the coupler 26 is of a low flow design, a cut-off feature is incorporated in the valve so as to prevent leakage

  fluid when disconnected.

  To avoid overloading the pump motor during the ventilation process, a thermally actuated circuit breaker (not shown) can be provided

  to monitor the current consumption of the motor 21.

  If a predetermined pressure is exceeded in the discharge hose 24, the increase in the current consumption by the motor 21 will cause the tripping of the circuit breaker and the supply of the motor.

21 will be interrupted.

  FIG. 7 shows an alternative embodiment of the dispensing device shown in FIG. 4, in which a foot valve 24 of the suction probe (connected to the coupler 12) and a safety valve 48 for return of liquid (mounted between the pipe 23 and a coupler 49) have been added to the device to prevent the liquid from returning to the supply tank 11 after temporary suspension of pumping. The valve 47 improves the precision of the device by preventing it from returning to the tank due to the bloating of the hose. discharge 24 and pressure equalization, while the normal drainage valve 48 is incorporated to allow the drainage function taking place when the motor is inverted and the line 23 is pressurized to avoid preloading of the valve spring 48 In some cases, it may be desirable to connect the safety valve 48 to the tank 11 via the

coupler 12.

  Having described the various devices of the present invention, we will now discuss in more detail some of the specific components. In particular, firstly in connection with FIGS. 8 to 13, the gear pump 20, as well as the reduction gear 22 and the drive motor 21 will be the subject of a discussion. The pump 20 is a pump of the involute spur gear type, with positive displacement. The pump comprises a body 50 and a cover 51 fixed to the body by a multitude of bolts to head 54 The cover 51 has a pair of holes 51 a and 51 b for connection to the suction hose 23

  and to the discharge hose 24, respectively.

  The pump body 50 and the cover 51 cooperate to define a chamber in which a pair of spur gears 55 and 56 are supported so as to be able to rotate The spur gear 55 is a drive gear and is keyed to a drive shaft 57 to avoid rotation of the gear relative to the shaft 57 The drive shaft 57 is supported so as to be able to rotate inside the pump body 50 by means of a bearing 60 supported by the body 50 As will be discussed, the gear 55 and the drive shaft 57 can be shifted slightly in the axial direction to ensure the correct positioning of the gear 55 inside the pump. One end of the drive shaft 57 extends into the reduction gear 22 A cartridge 63 containing double lip opposite seals 63 a and 63 b is supported by the pump body 50 and surrounds the outer surface of the drive shaft 57 The seals 63 a and 63 b form an effective seal when the associated chamber is at positive relative pressures

and negative, respectively.

  The spur gear 56 is an idler gear and is rotatably mounted on an idler shaft 64 and can also move axially along the shaft 64 to allow the gear 56 to be placed correctly inside the pump The idle shaft 64 is hollow and is inserted into a cylindrical cavity 65

  formed in the pump body 50.

  According to a feature of the present invention, an "movable" inner wear plate 69 and a "fixed" wear plate 70 are located on the sides

  opposite drive and idler gears 55 and 56.

  The wear plates 69 and 70 are made of a material with a low coefficient of friction such as carbon graphite which can be, for example, the so-called "Pure Carbon Il P 6038 C 2" type. The inner wear plate 69 , as shown in FIG. 12, is oval in shape with a pair of external recesses 69 a and 69 b formed on a first side of the plate which is opposite and in contact with the spur gears A pair of holes 69 c and 69 d is formed in the wear plate 69 so as to receive the drive shaft 57 and the idle shaft 64 respectively A third hole 69 e of small dimensions, the function of which will be explained, passing through the wear plate 69 , is located inside one of the surface recesses 69 a and 69 b, and is specifically shown in FIG. 12 inside the recess 69 a. The outer wear plate 70, as shown in FIG. 13 is epicyclic in shape, a pair of interior recesses 70 a and 70 b being formed in the side which is opposite and in contact with the spur gears The recesses 69 a, 69 b, 70 a and 70 b serve to release the pressure prevailing between the gear teeth during the operation of the pump A pair of holes 70 c and 70 d is formed in the wear plate 70 to allow the liquid to flow between the pump chamber and the pump ports 51 a and

b, respectively.

  The wear plate 69 is biased against the adjacent side walls of the spur gears 55 and 56 by an inner O-ring 71 a, which is disposed in a shoulder 69 f formed on the periphery of the inner wear plate 69 The seal 71 a stresses the inner wear plate 69 against the side walls of the spur gears As the spur gears 55 and 56 are mounted so as to be subjected to limited axial displacement, the force exerted by the inner O-ring 71 a also compresses the gears straight against the outer fixed wear plate 70 The hole 69 e provides the pressure equalization on each side of the plate 69 so as to ensure that the force urging the plate 69 against the gears is substantially exerted by the O-ring 71 a By minimizing the play around the gears of the pump, the possibilities of vacuum or of delivery head of the pump 20 are greatly increased In addition, by using carbon graphite to build the wear plates 69 and 70, the pump 20 can effectively run dry without additional lubrication.

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  As best seen in Figure 11, an outer O-ring 71b is disposed in a groove a formed in the surface of the outer end of the pump body 50 to form a seal between the pump body and the outer plate d 'fixed wear 70. Two O-rings 71 c and 71 d are arranged in circular grooves 70 e and 70 f formed in the outer wear plate 70, and serve to form a seal for

  the holes 51 a and 51 b of the cover, respectively.

  As shown in Figure 9, the spur gears 55 and 56, in conjunction with the pump body 50, cooperate to define separate left and right chambers 72 and 73, respectively, located on opposite sides of the spur gears Chamber 72 communicates with one of the holes 51 a of the cover (shown in dashes in Figure 9), while the chamber 73 communicates with the other hole 51 b of the cover (also shown in dashes in Figure 9) Depending on the particular rotation spur gears 55 and 56, one of the holes 51 a and 51 b serves as an input, while the other operates as an output For example, during operation, when the spur gears operate in direction A, as shown by the arrows in FIG. 9, the fluid located in the left chamber 72 will be entrained around the outside of the gears and introduced into the right chamber 73 Thus, during rotation in the direction A, the orifice 51 has the cover e constitutes an inlet while the other orifice 51 b is an outlet However, during rotation in the direction B, the orifice 51 a operates at the outlet while the other orifice 51 b serves as an inlet. As indicated above, the gear pump 20 is driven by the motor 21 via the reduction gear 22 The reduction gear, as best seen in FIG. 8, is of the conventional planetary gear type The reduction gear 22 is fixed to the pump body 50 by a multitude of bolts 77 Le

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  reducer 22 is driven by the motor shaft 80.

  The use of a planetary gear type reducer allows the shaft 80 of the motor and the shaft 57 of the pump drive to be aligned along a common axis. A target wheel 81 comprising a multitude of teeth formed on its circumference is mounted on the motor drive shaft 80 between the motor 21 and the reduction gear 22 The rotation sensor 33 is represented in FIG. 8 as a passive magnetic transducer 86 with variable reluctance, mounted in the lower part of the pump body 50 and having a pole piece 87 located in the vicinity of the periphery of the

teeth of the target wheel.

  Referring now to Figures 14 and, there is shown a valve structure which can function as a variant of the throttle valve

  23 'shown schematically in Figures 4, 5 and 7.

  As shown in FIG. 15, the valve has an external housing 90 made of plastic material. A conventional low-flow distribution coupler is shown in outline at 26, and is screwed

  on the lower part of the outer housing 90.

  The upper end of the housing 90 has a T-shaped portion 91 One end of the portion 91 is cylindrical in shape for insertion into the outer end of the discharge hose 24 and comprises a multitude of toothed pins 93 which engage in the inner surface of the hose 24 A ring 94 can be placed around the outside of the end of the hose to provide a safety attachment The other end 95 of the T-shaped portion 91 contains the

  vacuum rupture valve 36, which will be described below.

  The housing 90 of the valve has a central passage 96 for fluid which contains the anti-siphon check valve 27 In FIG. 15, the valve 27 is represented in the form of a mushroom-type valve, loaded by spring, comprising a mushroom 87 which comprises a hollow sleeve element 98 having one end which is slidably received inside a hollow central guide 99 The guide 99 comprises a multitude of radial openings 99 a which allow the flow of the fluid from the passage

  central 96 to the distribution coupler 26.

  The opposite end of the sleeve element 98 comprises an end cap 100 fixed by screwing, and cooperates with the sleeve element 98 to define an outer annular groove intended to receive an O-ring 101 A compression spring 102 serves to urge the mushroom 97 in a direction which causes the O-ring 101 to act against a conical sealing surface 103 formed in the upper part of the central passage 96 The cap defines a cylindrical part l O Qa extending axially, represented in FIG. 15 as having a length X, which is received by sliding inside a reduced diameter part formed at the top of the passage

  96 immediately above the conical surface 103.

  As previously indicated, the presence of the liquid in the throttle valve 25 ′ is monitored by the liquid detection switch 35. In FIG. 15, the switch 35 is represented in the form of a blade switch 104 screwed into a cavity 105 formed in the housing 90 The switch 104 responds to the movement of a magnet 106 placed inside the hollow sleeve element 98 The check valve 27 is designed, and the reed switch 104 and the magnet 106 are located, so that only the presence of a liquid causes the actuation of the switch 104 Thus, in operation, when the air pressure increases inside the discharge hose 24 relative to the pressure of the air in the central passage 96, the mushroom 97 will be moved slightly so as to raise the O-ring 101 relative to the surface 103, which allows the passage of air through the valve This slight movement does not

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  will not be done over an axial distance sufficient to cause actuation of the switch 104 However, the presence of a liquid in the fungus 97 has the effect that the latter moves the magnet 106 axially over a sufficient distance (approximately the distance X shown in Figure 15) to activate the switch 104 When the switch is actuated, the electronic control 30 knows that the liquid has reached the valve

  'and that the device has been booted.

  FIG. 15 also shows the various components of the vacuum rupture valve which

  allows the device to perform its drainage function.

  In particular, these components, which include the safety check valve 37 for reverse flow, the vacuum rupture valve 36 and the air filter 38, are housed inside a cavity formed in the end. 95 of the T-shaped part 91 of the housing 90 of the valve The cavity 110 is connected by a short passage 111 to the central passage 96 at a point located just above the mushroom 97 In FIG. 15, the check valve 37 is shown in the form of a conventional valve 112 of the ball type, which, when a positive pressure (relative to atmospheric pressure) is present in the passage 111, will be biased against a seat 113 The vacuum break valve 36 comprises a ball 114 which is urged against an O-ring 115 by a compression spring 116 The filter 38 comprises a screen 117 situated in the vicinity of the external end of the valve 36 A hollow threaded end plug 118 is provided to keep the components inside the

cavity 110.

  The throttle valve 25 of FIGS. 1 and 5 can have a structure essentially similar to that of the valve 25 ′ of FIG. 15, except that the components of the T-shaped part of the valve concerning the rupture characteristic of the vacuum do not

will not be included.

  While various embodiments of the present invention have been described, it will be appreciated that the features and embodiments can be combined or eliminated as necessary. For example, the device of Figure 5 can be modified to eliminate the drainage characteristic of plus, in some cases it may be desirable to replace the 25 or 25 'throttle valve with a valve / nozzle

  (not shown) held and operated by the user.

  In this case, the valve (nozzle) could be equipped with a trigger so as to be actuated manually by the user. The electronic control could be mounted so as to detect the actuation of the trigger, and control the pump in accordance with either with programmed instructions, either to dispense the liquid "on order", that is to say whenever

the trigger is actuated.

  It can therefore be seen that the present invention provides a very precise means of delivering predetermined quantities of liquid products under carefully controlled conditions. Furthermore, the device includes features to minimize the user's exposure to the product and to protect the environment against accidental leakage of

product.

  The present invention is not limited to the exemplary embodiments which have just been described, it is on the contrary liable to modifications and

  variants which will appear to those skilled in the art.

24 2669969

Claims (7)

  1 positive displacement gear pump (20) comprising a body (50) defining a chamber which communicates with first and second parts, a pair of spur gears (55, 56) rotatably supported inside the chamber and in engagement with each other, a separate wear plate (69; 70) located on each side of the spur gears, and means for urging the wear plates against one face   end of each of the spur gears.   2 Gear pump according to claim 1, characterized in that the wear plates are   made up of carbon grapitis.   3 gear pump according to claim 1, characterized in that the biasing means comprises an elastic O-ring (7 la; 71 b) disposed   between at least one of the wear plates and the body.   4 gear pump according to claim 1, characterized in that one of the wear plates (70) is fixed relative to the body and the other (69) of the plates and the spur gears are movable towards the plate fixed wear, and in that the biasing means exerts a biasing force against the movable wear plate (69) in the direction of the fixed wear plate so as to bias the plates against the adjacent end faces of each of the spur gears.   Gear pump according to claim 4, characterized in that it comprises an opening (69 e) extending through the movable wear plate (69) so as to equalize the pressure of the liquid in each side of this plate.   6 Gear pump according to claim 4, characterized in that the biasing means comprises an elastic O-ring disposed between the movable wear plate and body.   7 gear pump according to claim 1, characterized in that it comprises a shaft 2669969   reversible drive (57) supported in rotation relative to the body and connected so as to drive one of the spur gears, and a pair of seals (63 a, 63 b) supported relative to the body and in tight contact with the drive shaft, one of the seals serving to provide an effective seal around the shaft when the adjacent portion of the chamber is subjected to a relative positive pressure, and the other of the seals serving to provide an effective seal around the tree when the adjacent portion of the room   is subject to relative negative pressure.   8 Gear pump according to claim 7, characterized in that the pair of seals comprises facing lip seals.